The invention of this application relates to an improved fastener for roofing, particularly flat roofing of the single ply type or built-up roof type. In that context, roofing fasteners are used to fasten the insulation layer of the roofing to a perforated metal or wood deck, or the like. The use of mechanical fasteners can reduce the amount of shifting of the insulation which, in turn, avoids holes, splits, and cracks in a plastic roof membrane which overlies the insulation to prevent leakage. Thus the membrane integrity is better preserved, and the roof does not leak.
Additionally, a roof may be laid right over an old roof. In this circumstance, roofing fasteners may penetrate through the old roof into the deck. While metal decks are most typical, concrete decks are also used, or pre-formed wood fiber decks, gypsum decks, or the like. The roofing fasteners are screwed into whatever deck is present for retention of the upper layers.
The roofing fasteners of the prior art are typically made of steel. However, it is common for a significant amount of moisture to be present within the roof, underneath whatever protective moisture barrier coating is used. Particularly, when a new roof is put over an old roof, the old roofing materials may contain a significant amount of moisture, with the result that steel fasteners can face significant rusting conditions. Eventually, the fasteners may rust through and break, which can ultimately result in a failure of the roof system and possible blow-off.
In Patry, U.S. Pat. No. 4,003,175, a roofing fastener having a nonmetallic outer core is disclosed. This outer core may be made of plastic, for example polyvinylchloride, nylon, epoxy, polyurethane, or the like. However, because such plastics have generally exhibited insufficient strength to encounter stresses placed upon the roofing fastener during installation and afterwards, an inner metal core is provided. Such a structure is clearly rather expensive to manufacture, and is not immune from the effects of corrosion. For example, water can seep into the junction between the outer plastic portion and the core over the years, with ultimate rusting away of the core, resulting in a great decrease in fastener strength.
Forman, U.S. Pat. No. 2,993,950 shows another type of fastener having a metallic core element and a plastic outer body or casing.
In accordance with this present invention, a substantially nonmetallic fastener is provided, which may have an optional metal tip, but which is substantially nonmetallic along the majority of its length. Thus, a
nonmetallic fastener is provided which has adequate strength for use as a roofing fastener. Because the fastener is predominately nonmetallic, it is substantially immune to corrosion so that it does not lose its effectiveness over the years. Additionally, the preferred plastic itself of the fastener retains its strength in the presence of water to a degree better than other plastics such as nylon, for example, resulting in a high strength, long lasting, corrosion free roofing fastener, for providing roofs having extended useful lives.
Also, by the invention of this application a universal driver socket is provided to the fastener, to permit the fastener to be rotatably driven into a roof with a screwdriver or other driver of the Phillips, Allen, or conventional types.